1. Field of Invention
The present invention relates to a circuit protection device and protection method.
2. Related Art
The power supplier, such as the power converter or charger, is used to apply a stable voltage and/or current to a load. In order to provide a safety and qualified operation environment for the user and the electronic apparatus, a circuit protection device is configured in the power supplier. Accordingly, when the short circuit or over current is happened, the circuit protection device can limit the output power of the power supplier, and may further cease the operation of the power supplier. This function can prevent the permanent damage of the power supplier and the load connected with the power supplier.
As shown in FIG. 1A, a conventional circuit protection device 1 directly uses an operational amplifier to detect the current for determining whether the over current or short circuit happens or not. Although the conventional circuit protection device 1 has simple circuit design, it is not suitable for the power supplier with the rated output of a large current. In details, the threshold for enabling the conventional circuit protection device 1 is a constant value, and the circuit protection device 1 will be enabled after the over current excesses the threshold. Accordingly, for the power supplier with the rated output of a large current (e.g. larger than 150 A), the internal components of the power supplier and the load connected to the power supplier have been burdened with a huge stress before the enablement of the circuit protection device 1.
FIG. 1B is a schematic graph showing the waveform while the circuit protection device 1 is enabled, wherein the circuit protection device 1 is configured in a power supplier with the rated output current of 150 A. If the internal components of the power supplier or the load are malfunctioned (e.g. short circuit) before the power supplier starts to operate, the start current CS of the power supplier is an instantaneous large current. Besides, since the circuit protection device 1 is enabled after the start current CS reaches the threshold T, the components and load may be damaged due to the start current CS, which excesses the rated spec. This damage may further cause the danger of the user. In other words, in the power supplier with the conventional circuit protection device 1, the internal components and the load may be impacted by the larger stress, so that they are easily damaged and have shortened lifetime.
In addition, since the conventional circuit protection device 1 usually has simple circuit design, it does not have the latch and reset functions. This design restricts the application of the circuit protection device 1.
Therefore, it is an important subject of the invention to provide a circuit protection device and protection method that can decrease the threshold for enabling the protection function, so that the circuit protection device can fast respond to protect the power supplier, thereby minimizing the damage of the internal components and improving the reliability and utility.